NaCl stress on physio-biochemical metabolism and antioxidant capacity in germinated hulless barley (Hordeum vulgare L.)

Changes in physio-biochemical metabolism, phenolics and antioxidant capacity during germination of different wheat varieties

Changes in physio-biochemical metabolism, phenolics and antioxidant capacity during germination were studied in eight different wheat varieties. Results showed that germination enhanced sprout growth, and caused oxidative damage, but enhanced phenolics accumulation. Ferulic acid and p-coumaric acid were the main phenolic acids in wheat sprouts, and dihydroquercetin, quercetin and vitexin were the main flavonoids. The phenolic acid content of Jimai 44 was the highest on the 2th and 4th day of germination, and that of Bainong 307 was the highest on the 6th day. The flavonoid content of Hei jingang was the highest during whole germination. The enzymes activities of phenylalanine ammonia lyase (PAL), cinnamic acid 4-hydroxylase (C4H) and 4-coumarate coenzyme A ligase (4CL) were up-regulated. The activities of catalase, polyphenol oxidase and peroxidase were also activated. Antioxidant capacity of wheat sprouts was enhanced. The results provided new ideas for the production of naturally sourced phenolic rich foods.

Phenolic acids from medicinal and edible homologous plants: a potential anti-inflammatory agent for inflammatory diseases

Inflammation has been shown to trigger a wide range of chronic diseases, particularly inflammatory diseases. As a result, the focus of research has been on anti-inflammatory drugs and foods. In recent years, the field of medicinal and edible homology (MEH) has developed rapidly in both medical and food sciences, with 95% of MEH being associated with plants. Phenolic acids are a crucial group of natural bioactive substances found in medicinal and edible homologous plants (MEHPs). Their anti-inflammatory activity is significant as they play a vital role in treating several inflammatory diseases. These compounds possess enormous potential for developing anti-inflammatory drugs and functional foods. However, their development is far from satisfactory due to their diverse structure and intricate anti-inflammatory mechanisms. In this review, we summarize the various types, structures, and distribution of MEHP phenolic acids that have been identified as of 2023. We also analyze their anti-inflammatory activity and molecular mechanisms in inflammatory diseases through NF-κB, MAPK, NLRP3, Nrf2, TLRs, and IL-17 pathways. Additionally, we investigate their impact on regulating the composition of the gut microbiota and immune responses. This analysis lays the groundwork for further exploration of the anti-inflammatory structure-activity relationship of MEHP phenolic acids, aiming to inspire structural optimization and deepen our understanding of their mechanism, and provides valuable insights for future research and development in this field.

Melatonin mediates phenolic acids accumulation in barley sprouts under MeJA stress

Phenolic acids are secondary metabolites in higher plants, with antioxidant, anticancer, and anti-aging effects on the human body. Therefore, foods rich in phenolic acids are popular. Methyl jasmonate (MeJA) promoted phenolic acids accumulation but also inhibited sprout growth. Melatonin (MT) was a new type of plant hormone that not only alleviated plants' abiotic stress, but also promoted the synthesis of plant-stimulating metabolism. This study aimed to elucidate the mechanism of exogenous MT on the growth and development, and phenolic acids metabolism of barley sprouts under MeJA treatment. The results showed that MT increased the phenolic acids content in sprouts by increasing the activities of phenylalanine ammonia-lyase and cinnamic acid 4-hydroxylase, and up-regulating the gene expression of phenylalanine ammonia-lyase, cinnamic acid 4-hydroxylase, 4-coumarate: coenzyme a ligase, and ferulic acid-5-hydroxylase. MT attenuated the growth inhibition of barley sprouts under MeJA stress by increasing the activities of regulated antioxidant enzymes and the expression of their corresponding genes. Furthermore, MT increased the NO content and induced Ca2+ burst in barley sprouts under MeJA stress. These events were inhibited by DL-4-Chlorophenylalanine. These results suggested that MT ameliorated growth inhibition and promoted the biosynthesis of phenolic acids in barley sprouts under MeJA stress.

Methyl Jasmonate and Zinc Sulfate Induce Secondary Metabolism and Phenolic Acid Biosynthesis in Barley Seedlings

This study aimed to reveal the impact of MeJA and ZnSO4 treatments on the physiological metabolism of barley seedlings and the content of phenolic acid. The results showed that MeJA (100 μM) and ZnSO4 (4 mM) treatments effectively increased the phenolic acid content by increasing the activities of phenylalanine ammonia-lyase and cinnamate-4-hydroxylase (PAL) and cinnamic acid 4-hydroxylase (C4H) and by up-regulating the expression of genes involved in phenolic acid synthesis. As a result of the MeJA or ZnSO4 treatment, the phenolic acid content increased by 35.3% and 30.9% at four days and by 33.8% and 34.5% at six days, respectively, compared to the control. Furthermore, MeJA and ZnSO4 treatments significantly increased the malondialdehyde content, causing cell membrane damage and decreasing the fresh weight and seedling length. Barley seedlings responded to MeJA- and ZnSO4-induced stress by increasing the activities of antioxidant enzymes and controlling their gene expression levels. Meanwhile, MeJA and ZnSO4 treatments significantly upregulated calcium-adenosine triphosphate, calmodulin-dependent protein kinase-related kinase, and calmodulin-dependent protein genes in barley seedlings. This suggested that Ca2+ may be the signaling molecule that promotes phenolic acid synthesis under MeJA and ZnSO4 treatment. This study deepens the understanding of the phenolic acid enrichment process in barley seedlings under MeJA and ZnSO4 treatments.

Refrigerated storage stimulates isoflavone and γ-aminobutyric acid accumulation in germinated soybeans

This study aims to investigate the quality changes of germinated soybeans during refrigerated storage (4 °C), with an emphasis on the stimulatory effect of refrigeration on their special functional compounds. After germinating for two days, germinated soybeans were stored at 4 °C for seven days, while the germinated soybeans stored at 25 °C served as control group. The results showed that refrigerated storage significantly affected the physiological changes in germinated soybeans. The weight loss rate, browning rate, malondialdehyde (MDA) content and H2O2 content all decreased dramatically during refrigerated storage compared to the control group. The total phenolic and total flavonoid contents of germinated soybeans under refrigeration exhibited a trend of increasing and then decreasing over time. Additionally, during refrigerated storage, the total isoflavone content reached a peak of 8.72 g/kg on the fifth day, in which the content of daidzein and glycitin increased by 45% and 49% respectively, when compared with the control group. Moreover, the content of γ-aminobutyric acid (GABA) peaked on the first day, and kept a high level during storage. In which, the refrigerated group was 2.35-, 2.88-, 1.67-fold respectively after storage for three to seven days. These results indicated that refrigeration stimulated the biosynthesis of isoflavones and GABA in germinated soybeans during storage. More importantly, there was a sequential difference in the timing of the stimulation of the two functional components under refrigeration.

Mechanisms on salt tolerant of Paenibacillus polymyxa SC2 and its growth-promoting effects on maize seedlings under saline conditions

Soil salinity negatively affects microbial communities, soil fertility, and agricultural productivity and has become a major agricultural problem worldwide. Plant growth-promoting rhizobacteria (PGPR) with salt tolerance can benefit plant growth under saline conditions and diminish the negative effects of salt stress on plants. In this study, we aimed to understand the salt-tolerance mechanism of Paenibacillus polymyxa at the genetic and metabolic levels and elucidate the mechanism of strain SC2 in promoting maize growth under saline conditions. Under salt stress, we found that strain SC2 promoted maize seedling growth, which was accompanied by a significant upregulation of genes encoding for the biosynthesis of peptidoglycan, polysaccharide, and fatty acid, the metabolism of purine and pyrimidine, and the transport of osmoprotectants such as trehalose, glycine betaine, and K+ in strain SC2. To further enhance the salt resistance of strain SC2, three mutants (SC2-11, SC2-13, and SC2-14) with higher capacities for salt resistance and exopolysaccharide synthesis were obtained via atmospheric and room-temperature plasma mutagenesis. In saline-alkaline soil, the mutants showed better promoting effect on maize seedlings than wild-type SC2. The fresh weight of maize seedlings was increased by 68.10% after treatment with SC2-11 compared with that of the control group. The transcriptome analysis of maize roots demonstrated that SC2 and SC2-11 could induce the upregulation of genes related to the plant hormone signal transduction, starch and sucrose metabolism, reactive oxygen species scavenging, and auxin and ethylene signaling under saline-alkaline stress. In addition, various transcription factors, such as zinc finger proteins, ethylene-responsive-element-binding protein, WRKY, myeloblastosis proteins, basic helix-loop-helix proteins, and NAC proteins, were up-regulated in response to abiotic stress. Moreover, the microbial community composition of maize rhizosphere soil after inoculating with strain SC2 was varied from the one after inoculating with mutant SC2-11. Our results provide new insights into the various genes involved in the salt resistance of strain SC2 and a theoretical basis for utilizing P. polymyxa in saline-alkaline environments.

Germination and Growth Characteristics of nud Knockout and win1 Knockout Barley Lines under Salt Stress

Hordeum vulgare genes NUD (HvNUD) and WIN1 (HvWIN1) play a regulatory role in cuticle organization. Because the cuticle is a key evolutionary acquisition of plants for protection against environmental factors, a knockout (KO) of each gene may alter their ability to adapt to unfavorable conditions. A potential pleiotropic effect of HvNUD or HvWIN1 gene mutations can be assessed under salt stress. Initial developmental stages are the most sensitive in living organisms; therefore, we evaluated salt tolerance of nud KO and win1 KO barley lines at the seedling stage. Air-dried barley grains of the KO lines and of a wild-type (WT) line were germinated in NaCl solutions (50, 100, or 150 mM). Over 30 physiological and morphological parameters of seedlings were assessed. Potential pleiotropic effects of the HvNUD gene KO under salt stress included the stimulation of root growth (which was lower under control conditions) and root necrosis. The pleiotropic effects of the HvWIN1 gene KO under the stressful conditions manifested themselves as maintenance of longer root length as compared to the other lines; stable variation of most of morphological parameters; lack of correlation between root lengths before and after exposure to NaCl solutions, as well as between shoot lengths; and the appearance of twins. Salt tolerance of the analyzed barley lines could be ranked as follows: nud KO > win1 KO ≈ WT, where nud KO lines were the most salt-tolerant. A comparison of effects of salinity and ionizing radiation on nud KO and win1 KO barley lines indicated differences in tolerance of the lines to these stressors.

COI1 dependent jasmonic acid signalling positively modulates ROS scavenging system in transgenic hairy root culture of tomato

Reactive oxygen species (ROS) production is a routine event in plants. ROS function as signalling molecules in regulating plant development and defence. However, their accumulation beyond threshold leads to toxicity. Hence, plants are evolved with specialized ROS scavenging system involving phytohormones (synthesis and signalling), enzymes and metabolites. To understand the role of phytohormone jasmonic acid (JA) signalling in ROS scavenging, tomato coronatine insensitive 1 (SlCOI1), a key gene in JA signalling, was silenced and overexpressed in tomato transgenic hairy roots (HR) under the constitutive promoter. Targeted metabolomics of transgenic HR revealed accumulation of phenolic acids including ferulic acid, coumaric acid, vanillic acid, and flavonoid catechin in SlCOI1 overexpressed line. Moreover, osmolyte amino acids proline, asparagine, and glutamine showed a positive co-relation with transgenic overexpression of SlCOI1. Ascorbic acid-glutathione, a crucial antioxidant system was found to be influenced by COI1-mediated JA signalling. The expression of genes encoding enzymes superoxide dismutase 1, ascorbate peroxidase 1, and dehydroascorbate reductase 2 was found to be down and upregulated in SlCOI1 silenced and overexpressed lines, respectively. Methyl jasmonate and Fusarium oxysporum f.sp. lycopersici crude extract treatment further confirmed the regulatory role of COI1-mediated JA signalling in regulation of enzymatic components involved in ROS scavenging. The COI1-mediated JA signalling could also elevate the expression of RESPIRATORY BURST OXIDASE HOMOLOG-B gene which is involved in ROS wave signal generation. The present study underscores the role of COI1-mediated JA signalling in modulating enzymatic and non-enzymatic components of ROS scavenging system and pathogen associated molecular pattern triggered immunity.

Antioxidant Benefits and Potential Mechanisms of Slightly Acidic Electrolyzed Water Germination in Sesame

Slightly acidic electrolytic water (SAEW) treatment for seed germination is a promising technique for sustainable agriculture. This study investigated the antioxidant activity of germinated sesame seeds treated with SAEW for the first time. Specifically, the impact and correlation of SAEW on the activities of total phenols, total flavonoids, and antioxidant oxidase in sesame seeds were examined. The results showed that SAEW with low ACC inhibited sesame germination, SAEW with high ACC promoted sesame germination, and sesame buds treated with SAEW with 30 mg/L and 50 mg/L ACC showed lower antioxidant activity and total phenolic and flavone content compared to tap water. In contrast, SAEW with 30 mg/L ACC had no significant effect on sesame growth but positively influenced the antioxidant activity of sesame seed germination by promoting phenolic compound synthesis through increased phenylalanine ammonia-lyase (PAL) activity and enhancing antioxidant activity by boosting PAL, polyphenol oxidase (PPO), and peroxidase (POD) activities. Generally, antioxidant ability was the most prominent in SAEW with 30 mg/L ACC, and positive correlations between antioxidation and total phenols and flavonoids content were found in sesame. These findings provide valuable insights into the mechanisms underlying the enhanced antioxidant capacity observed in germinated sesame seeds under SAEW stress.

Salicylic Acid and α-Tocopherol Ameliorate Salinity Impact on Wheat

Background: Soil salinity negatively impacts agricultural productivity. Consequently, strategies should be developed to inculcate a salinity tolerance in crops for sustainable food production. Growth regulators play a vital role in regulating salinity stress tolerance. Methods: Thus, we examined the effect of exogenous salicylic acid (SA) and alpha-tocopherol (TP) (100 mg/L) on the morphophysio-biochemical responses of two wheat cultivars (Pirsabak-15 and Shankar) to salinity stress (0 and 40 mM). Results: Both Pirsabak-15 and Shankar cultivars were negatively affected by salinity stress. For instance, salinity reduced growth attributes (i.e., leaf fresh and dry weight, leaf moisture content, leaf area ratio, shoot and root dry weight, shoot and root length, as well as root-shoot ratio), pigments (chlorophyll a, chlorophyll a, and carotenoids) but increased hydrogen peroxide (H₂O₂), malondialdehyde (MDA), and endogenous TP in both cultivars. Among the antioxidant enzymes, salinity enhanced the activity of peroxidase (POD) and polyphenol oxidase (PPO) in Pirsabak-15; glutathione reductase (GR) and PPO in Shankar, while ascorbate peroxidase (APOX) was present in both cultivars. SA and TP could improve the salinity tolerance by improving growth and photosynthetic pigments and reducing MDA and H₂O₂. In general, the exogenous application did not have a positive effect on antioxidant enzymes; however, it increased PPO in Pirsabak-15 and SOD in the Shankar cultivar. Conclusions: Consequently, we suggest that SA and TP could have enhanced the salinity tolerance of our selected wheat cultivars by modulating their physiological mechanisms in a manner that resulted in improved growth. Future molecular studies can contribute to a better understanding of the mechanisms by which SA and TP regulate the selected wheat cultivars underlying salinity tolerance mechanisms.

Spermidine alleviates oxidative damage and enhances phenolic compounds accumulation in barley seedlings under UV-B stress

BACKGROUND

Ultraviolet B (UV-B) radiation can enhance the accumulation of phenolic compounds (PCs) in barley seedling, although this may result in severe oxidative damage. In the present study, the role of spermidine in alleviating oxidative damage and regulating synthesis of PCs in barley seedlings under UV-B stress was investigated.

RESULTS

Exogenous spermidine increased the length and fresh weight as well as PCs contents of barley seedlings under UV-B stress. Application of dicyclohexylamine, an inhibitor of endogenous spermidine synthesis, significantly inhibited the growth and PC accumulation of barley seedlings under UV-B stress, although this inhibitory effect can be alleviated by exogenous spermidine. Exogenous spermidine increased the contents of vanillic acid, syringic acid, protocatechuic acid and p-coumaric acid in barley seedlings under UV-B stress by 20-200% through enhancing the activities of enzymes related to synthesis of these acids. In addition, exogenous spermidine enhanced activities and gene expression of antioxidant enzymes in barley seedlings under UV-B stress, including peroxidase, glutathione reductase and glutathione S-transferase.

CONCLUSION

Spermidine can alleviate oxidative damage of barley seedlings under UV-B stress and enhance the accumulation of PCs. © 2022 Society of Chemical Industry.

Exogenous γ-aminobutyric acid (GABA) mitigated salinity-induced impairments in mungbean plants by regulating their nitrogen metabolism and antioxidant potential

BACKGROUND

Increasing soil salinization has a detrimental effect on agricultural productivity.Therefore, strategies are needed to induce salinity-tolerance in crop species for sustainable foodproduction. γ-aminobutyric acid (GABA) plays a key role in regulating plant salinity stresstolerance. However, it remains largely unknown how mungbean plants (Vigna radiata L.) respondto exogenous GABA under salinity stress.

METHODS

Thus, we evaluated the effect of exogenous GABA (1.5 mM) on the growth and physiobiochemicalresponse mechanism of mungbean plants to saline stress (0-, 50-, and 100 mM [NaCland Na2SO4, at a 1:1 molar ratio]).

RESULTS

Increased saline stress adversely affected mungbean plants' growth and metabolism. Forinstance, leaf-stem-root biomass (34- and 56%, 31- and 53%, and 27- and 56% under 50- and 100mM, respectively]) and chlorophyll concentrations declined. The carotenoid level increased (10%)at 50 mM and remained unaffected at 100 mM. Hydrogen peroxide (H2O2), malondialdehyde(MDA), osmolytes (soluble sugars, soluble proteins, proline), total phenolic content, andenzymatic activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), peroxidase(POD), glutathione reductase (GTR), and polyphenol oxidation (PPO) were significantlyincreased. In leaves, salinity caused a significant increase in Na+ concentration but a decrease inK+ concentration, resulting in a low K+/Na+ concentration (51- and 71% under 50- and 100- mMstress). Additionally, nitrogen concentration and the activities of nitrate reductase (NR) andglutamine synthetase (GS) decreased significantly. The reduction in glutamate synthase (GOGAT)activity was only significant (65%) at 100 mM stress. Exogenous GABA decreased Na+, H2O2,and MDA concentrations but enhanced photosynthetic pigments, K+ and K+/Na+ ratio, Nmetabolism, osmolytes, and enzymatic antioxidant activities, thus reducing salinity-associatedstress damages, resulting in improved growth and biomass.

CONCLUSION

Exogenous GABA may have improved the salinity tolerance of mungbean plants by maintaining their morpho-physiological responses and reducing the accumulation of harmfulsubstances under salinity. Future molecular studies can contribute to a better understanding of themolecular mechanisms by which GABA regulates mungbean salinity tolerance.

Effects of methyl jasmonate and NaCl treatments on the resveratrol accumulation and defensive responses in germinated peanut (Arachis hypogaea L.)

In this study, the effects of methyl jasmonate (MeJA) and sodium chloride (NaCl) treatments on the resveratrol biosynthesis and physiology of peanuts during germination were investigated. The results showed that MeJA (150 μM) and NaCl (150 mM) treatments significantly promoted resveratrol biosynthesis in germinated peanuts. MeJA and NaCl treatments promoted resveratrol accumulation by regulating the activities of phenylalanine ammonia lyase (PAL), cinnamic acid 4-hydroxylase (C4H) and 4-coumarate coenzyme A ligase (4CL) and their gene expression levels in cotyledons and non-cotyledons. In addition, both MeJA and NaCl treatments inhibited peanut sprout growth, as evidenced by shorter sprout length, increased malondialdehyde content, and accumulation of reactive oxygen species in cotyledons and non-cotyledons. Both treatments' germinated peanuts responded to the environmental stimuli by raising the activities of antioxidant enzymes and controlling the levels of their gene' expression. Meanwhile, MeJA and NaCl treatments promoted Ca²⁺ aggregation in the root tips. Therefore, it can be deduced that Ca²⁺ may help improve the plant's resistance to adversity. In conclusion, treatment with MeJA (150 μM) or NaCl (150 mM) during germination is an effective way to enrich the resveratrol content of peanuts. Germinated peanuts enhance adaptation to the external environment by promoting resveratrol biosynthesis and enhancing antioxidant systems.

Adaptive Response and Transcriptomic Analysis of Flax (Linum usitatissimum L.) Seedlings to Salt Stress

Soil salinity constrains agricultural development in arid regions. Flax is an economically important crop in many countries, and screening or breeding salinity-resistant flax cultivars is necessary. Based on the previous screening of flaxseed cultivars C71 (salt-sensitive) and C116 (salt-tolerant) as test materials, flax seedlings stressed with different concentrations of NaCl (0, 100, 150, 200, and 250 mmol/L) for 21 days were used to investigate the effects of salt stress on the growth characteristics, osmotic regulators, and antioxidant capacity of these flax seedlings and to reveal the adaptive responses of flax seedlings to salt stress. The results showed that plant height and root length of flax were inhibited, with C116 showing lower growth than C71. The concentrations of osmotic adjustment substances such as soluble sugars, soluble proteins, and proline were higher in the resistant material, C116, than in the sensitive material, C71, under different concentrations of salt stress. Consistently, C116 showed a better rapid scavenging ability for reactive oxygen species (ROS) and maintained higher activities of antioxidant enzymes to balance salt injury stress by inhibiting growth under salt stress. A transcriptome analysis of flax revealed that genes related to defense and senescence were significantly upregulated, and genes related to the growth and development processes were significantly downregulated under salt stress. Our results indicated that one of the important adaptations to tolerance to high salt stress is complex physiological remediation by rapidly promoting transcriptional regulation in flax.

Mechanism of calcium in melatonin enhancement of functional substance-phenolic acid in germinated hulless barley

Phenolic acid is a physiologically active substance that has a variety of effects on humans. Barley sprouts are often used as food ingredients to enrich phenolic acids and to further produce functional foods rich in phenolic acids. In this study, the mechanism of Ca²⁺ involvement in regulating phenolic acid biosynthesis and plant growth in barley by melatonin (MT) under NaCl stress was investigated. According to the studies, MT (25 μM) increased total calcium content, induced Ca²⁺ burst, and up-regulated the gene expression of calcium-regulated protein-dependent protein kinase and calcium-binding protein transcription-activating protease in NaCl-stressed (60 mM) barley. Exogenous MT and its combined CaCl₂ (0.4 mM) significantly promoted phenolic acid biosynthesis by increasing the activity of C4H and PAL, and induced gene expression of PAL and F5H. The addition of exogenous CaCl₂ and MT caused systemic tolerance in NaCl-stressed barley, as determined by a decrease in the fluorescence intensity of hydrogen peroxide and oxygen radical anions as well as an enhancement in the antioxidant enzyme, thus significantly increasing sprout length and fresh weight. In addition, combined use of MT with Ca²⁺ antagonists (lanthanum chloride or ethylene glycol tetraacetic acid), impaired all impacts as mentioned above. These findings imply that Ca²⁺ participated in MT-induced phenolic acid biosynthesis and growth improvement in NaCl-stressed barley.

Transcriptomic and Metabolomic Analyses Reveal the Differential Regulatory Mechanisms of Compound Material on the Responses of Brassica campestris to Saline and Alkaline Stresses

Oilseed rape not only has the function of improve saline and alkaline soils, but also alleviate the local feed shortage. However, medium- and high-degree soil salinization and alkalinization always inhibit the growth of oilseed rape. Studies have shown that compound material can improve the tolerance to saline and alkaline stress of crops, but the difference in the regulation mechanism of compound material on oilseed rape in saline and alkaline soils is not clear. This study explored the difference through determining the leaf ion contents, physiological indexes, transcriptomics, and metabolomics of oilseed rape in salinized soil (NaCl 8 g kg^-1) and alkalinized soil (Na₂CO₃ 8 g kg^-1) at full flowering stage, respectively after the application of compound material. The results showed that in salinized and alkalinized soil, the compound material upregulated the genes related to the regulation of potassium ion transport, and changed the amino acid metabolic pathway, which reduced the contents of Na⁺, malondialdehyde (MDA), and relative conductivity (REC) in leaves, and increased the contents of K⁺ and Mg²⁺ and the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT). However, there were differences in the regulation mechanism of compound material in salinized and alkalinized soil. In salinized soil, the compound material improved the tolerance of oilseed rape to saline stress by upregulating transcription factors mannose-1-phosphate guanylyltransferase (GPMM) and Glutamine--fructose-6-phosphate transaminase (GFPT) and downregulating phosphomannomutase (PMM) to change nucleotide metabolism pathway and lipid metabolism pathway. In alkalized soil, the compound material improved the tolerance of oilseed rape to alkaline stress by upregulating transcription factors Phenylalanine ammonia lyase (PAL) to change the biosynthesis pathway of other secondary metabolites. Therefore, the compound material can improve the tolerance of oilseed rape to saline and alkaline stress by regulating the genetic adaptability and apparent plasticity, but the mechanisms were different. This study provides a practical method for the ecological environment restoration and the development of animal husbandry.

Role of exogenous melatonin involved in phenolic acid metabolism of germinated hulless barley under NaCl stress

In this study, the effects of exogenous MT on phenolic acids biosynthesis and the response to NaCl stress in germinating barley were investigated to explicate the role and molecular mechanism of MT in the regulation of phenolic acids and biomass under salt stress. Results showed that exogenous MT increased the gene expression and activities of phenylalanine ammonia lyase and cinnamate 4-hydroxylase involved in phenols biosynthesis. As a result, phenolic acids contents significantly increased, and ferulic acid, p-coumaric acid and p-hydroxybenzoic acid were mostly induced by exogenous MT treatment. Meanwhile, exogenous MT application reduced the damage of NaCl stress, including promotion sprout growth, biomass and Ca²⁺ influs, malonaldehyde and H₂O₂ content reduction, increases of peroxidase, superoxide dismutase and catalase activities in barley seedlings. These results indicated that exogenous MT was essential for inducing phenolic acids accumulation and alleviated the inhibition of NaCl stress on barley seedlings.

Effect of γ-aminobutyric Acid on Phenolics Metabolism in Barley Seedlings under Low NaCl Treatment

It has been revealed that high NaCl stress (>60 mmol L^-1) induced phenolics accumulation in barley seedlings, with γ-aminobutyric acid (GABA) playing a key role. Interestingly, low NaCl stimulus (20 mmol L^-1) enhancing phenolics synthesis and growth of barley seedlings was also reported recently. Hence, exogenous GABA and its bio-synthesis inhibitor 3-mercaptopropionic acid (3-MP) were applied to reveal the mechanism of GABA regulating phenolics metabolism in barley seedlings treated with 20 mmol L^-1 NaCl. The contents of total phenolics and flavonoids significantly increased by 11.64% and 14.52% under NaCl, respectively. The addition of GABA further increased phenolics and flavonoids contents, especially for gallic acid, protocatechuic acid, caffeic acid, and quercetin, compared with NaCl treatment. Simultaneously, GABA increased the activities and mRNA levels of phenylalanine ammonia lyase (PAL), cinnamic acid 4-hydroxylase (C4H), and 4-coumalyl CoA ligase (4CL). The addition of 3-MP suppressed the above effects, except for increasing the protein levels of PAL, C4H, and 4CL. Low concentration of NaCl not only promoted growth, but also stimulated endogenous GABA metabolism to affect key enzymes activities and mRNA levels for phenolics synthesis in barley seedlings.

GABA Regulates Phenolics Accumulation in Soybean Sprouts under NaCl Stress

NaCl stress causes oxidative stress in plants; γ-aminobutyric acid (GABA) could alleviate such abiotic stress by enhancing the synthesis of phenolics, but the underlying mechanism is not clear. We investigated the effects of GABA on phenolics accumulation in soybean sprouts under NaCl stress by measuring changes in the content of physiological biochemicals and phenolic substances, in the activity and gene expression of key enzymes, and in antioxidant capacity. GABA reduced the oxidative damage in soybean sprouts caused by NaCl stress and enhanced the content of total phenolics, phenolic acids, and isoflavones by 16.58%, 22.47%, and 3.75%, respectively. It also increased the activities and expression of phenylalanine ammonia lyase, cinnamic acid 4-hydroxylase, and 4-coumarate coenzyme A ligase. Furthermore, GABA increased the activity of antioxidant enzymes and the antioxidant capacity. These events were inhibited by 3-mercaptopropionate (an inhibitor for GABA synthesis), indicating that GABA mediated phenolics accumulation and antioxidant system enhancement in soybean sprouts under NaCl stress.

Transcriptome Analysis Reveals Genes of Flooding-Tolerant and Flooding-Sensitive Rapeseeds Differentially Respond to Flooding at the Germination Stage

Flooding results in significant crop yield losses due to exposure of plants to hypoxic stress. Various studies have reported the effect of flooding stress at seedling establishment or later stages. However, the molecular mechanism prevailing at the germination stage under flooding stress remains enigmatic. The present study highlights the comparative transcriptome analysis in two rapeseed lines, i.e., flooding-tolerant (Santana) and -sensitive (23651) lines under control and 6-h flooding treatments at the germination stage. A total of 1840 up-regulated and 1301 down-regulated genes were shared by both lines in response to flooding. There were 4410 differentially expressed genes (DEGs) with increased expression and 4271 DEGs with reduced expression shared in both control and flooding conditions. Gene ontology (GO) enrichment analysis revealed that “transcription regulation”, “structural constituent of cell wall”, “reactive oxygen species metabolic”, “peroxidase”, oxidoreductase”, and “antioxidant activity” were the common processes in rapeseed flooding response. In addition, the processes such as “hormone-mediated signaling pathway”, “response to organic substance response”, “motor activity”, and “microtubule-based process” are likely to confer rapeseed flooding resistance. Mclust analysis clustered DEGs into nine modules; genes in each module shared similar expression patterns and many of these genes overlapped with the top 20 DEGs in some groups. This work provides a comprehensive insight into gene responses and the regulatory network in rapeseed flooding stress and provides guidelines for probing the underlying molecular mechanisms in flooding resistance.

Comprehensive Evaluation of the Effect of Ultraviolet Stress on Functional Phytochemicals of Hulless Barley (Qingke) Grass in Different Growth Times at Vegetative Stage

The present study was executed to analyze the functional phytochemicals of hulless barley grass grown under different intensities of ultraviolet stress. The wheat seedlings were imposed to 0.5, 1.0, 1.5, 2.0, and 2.5 h ultraviolet radiation and harvested in different times at vegetative stage. Specifically, the contents of total polyphenols, total flavonoids, total triterpenes, total polysaccharides, proanthocyanidins, and chlorophyll were determined and antioxidants capacity was evaluated by OH^• and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) scavenging ability. A mathematical model (Technique for Order Preference by Similarity to Ideal Solution, TOPSIS) was also employed for the comprehensive evaluation of functional components of hulless barley grass at different growth stages. The results showed that the UV stress could efficiently improve/preserve the contents of total polyphenols, total flavonoids, total triterpenes, total polysaccharides, proanthocyanidins, chlorophyll a, chlorophyll b, and total chlorophyll, as well as the OH^• and ABTS scavenging capacity. TOPSIS evaluation revealed that the highest phytochemical contents were yield on the 15th day under 1.0 h ultraviolet treatment.

NaCl treatment on physio-biochemical metabolism and phenolics accumulation in barley seedlings

Phenolics are important secondary metabolites in plants with strong antioxidant effects. Seeds germination and exogenous stimulation could activate endogenous enzymes to enhance the content of phenolic acids and flavonoids. Barley seeds geminated under NaCl (1-20 mM) treatment to evaluate the accumulation of phenolics in this study. Results showed that NaCl treatment significantly enhanced the growth of seedlings, especially bud length. NaCl treatment up-regulated genes and proteins expression of phenylalanine ammonia lyase (PAL), cinnamate-4-hydroxylase (C4H) and 4-coumarate-CoA ligase (4CL), resulting in the enhancement of their activities. As a result, phenolic acids and flavonoids contents increased by 11.19% and 32.54%, respectively, in which gallic acid, protocatechuic, fisetin, myricetin and quercetin were affected mostly. Moreover, NaCl treatment enhanced 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging capacity. Hence, NaCl stimulated the synthesis of phenolic components via enhancing gene, protein expression and the activity of key enzymes.

Fraxinus mandshurica 4-coumarate-CoA ligase 2 enhances drought and osmotic stress tolerance of tobacco by increasing coniferyl alcohol content

4-Coumarate-CoA ligase (4CL) is an important branch point in the phenylpropane pathway and plays important roles in plant growth and development. In this study, the 4CL2 gene from Fraxinus mandshurica (designated Fm4CL2) was identified and isolated. Sequence analysis revealed that Fm4CL2 is a type I 4CL gene involved in lignin biosynthesis. Analysis of cell wall components revealed that Fm4CL2-overexpressing (OE-Fm4CL2) tobacco showed increased lignin content (by 58.9%) and decreased hemicellulose content (by 41.2%). Detection of small-molecule metabolites in the lignin pathway revealed that coumaric acid content decreased by 48% and coniferyl alcohol content increased by 250% compared with the control values. Compared with wild type, OE-Fm4CL2 tobacco showed increased xylem cell layer number (by 120%) and cell wall thickness (by 54.5%). Under osmotic stress, transgenic tobacco showed higher growth than wild-type tobacco. The germination rate of transgenic tobacco was higher than that of wild type. Reactive oxygen species accumulation and malondialdehyde content were significantly lower in transgenic tobacco than in wild type. Under drought, the expression of stress-related genes was higher in 35S-Fm4CL2-infected Fraxinus mandshurica plants than in control plants. These results indicate that Fm4CL2 overexpression can enhance drought and osmotic stress tolerance of plants.

Effects of White LED Light and UV-C Radiation on Stilbene Biosynthesis and Phytochemicals Accumulation Identified by UHPLC-MS/MS during Peanut (Arachis hypogaea L.) Germination

In this study, the effects of white light-emitting diode (LED) and UV-C radiation (with the same intensity) on stilbene biosynthesis and phytochemicals accumulation of peanut sprouts were investigated. Results showed that white light radiation promoted the growth of peanut sprouts while UV-C radiation had the opposite effect. Contents of total phenolics, total flavonoids, and phytochemicals significantly increased in peanut sprouts treated by white light or UV-C radiation. Besides, light radiation significantly induced stilbene accumulation by upregulating the expression of genes and enzymes in stilbene biosynthesis-related pathway, and UV-C was more effective to promote stilbene accumulation. Compared with piceid and piceatannol, resveratrol showed the highest accumulation in peanut sprouts treated by light radiation. In summary, white light or UV-C radiation could be used as a method to promote stilbene biosynthesis and phytochemicals accumulation in peanut sprouts and UV-C was more effective.

Liquiritin elicitation can increase the content of medicinally important glucosinolates and phenolic compounds in Chinese kale plants

BACKGROUND

Brassica oleracea var. alboglabra (Chinese kale) is an important vegetable grown in southern China. This study was aimed at searching for environmentally friendly and affordable approaches to increase the production of medicinally relevant glucosinolates and phenolic compounds in Chinese kale plants. For this purpose, the foliar application of liquiritin at 0 (control), 250, 500 and 750 ppm was tested starting from the four-leaf stage and repeated every two weeks until plants were two months old.

RESULTS

Foliar application of liquiritin in Chinese kale plants significantly increased glucosinolates and total phenolic content, in a dose-dependent manner. Compared with control plants, 2.3- and 1.9-fold increases in yields of glucosinolates and total phenolic content, respectively, were corroborated in Chinese kale plants treated with 750 ppm of liquiritin. Along with rises in the content of eight different glucosinolates, liquiritin elicitation effectively increased the concentration of glycosilated and acylated flavonoids and hydroxycinnamic acids. The expression of genes involved in glucosinolate and phenolic biosynthesis was significantly higher in liquiritin-treated plants as compared to controls.

CONCLUSIONS

Liquiritin elicitation is a feasible and environmentally friendly practice for increasing the production of medicinally important glucosinolates and phenolic compounds in Chinese kale, which may improve this plant's value as a nutraceutical food. This study also contributes to understanding the molecular mechanisms underlying liquiritin elicitation. This is the first report documenting the use of liquiritin for an elicitation purpose in plants. © 2019 Society of Chemical Industry.